Energy harvesting from sediment microbial fuel cell to supply uninterruptible regulated power for small devices

Sediment microbial fuel cell (SMFC) is a bio‐electrochemical device that generates direct current by microbes present in the soil. The main drawback of SMFC is the low voltage and fluctuations. Therefore, a suitable scheme is required to obtain sufficient voltage with insignificant fluctuation. This paper proposes an energy harvester power management system (PMS) to get rid of low voltage and fluctuation problem of SMFC. The proposed PMS is composed of a dc‐dc boost converter, switches, and super capacitors. The boost converter (using LTC3108 IC) successfully steps up the voltage up to 2.658 V and provides it to the load for 1.5 minutes. Four SMFCs connected with four individual super capacitors and a single boost converter has been used to implement this scheme. In this strategy, the charging and discharging time of the SMFCs are controlled in such a way that the continuous power will be supplied to the load with the optimum number of SMFCs. This scheme is tested on an experimental setup. It is found that the energy harvester PMS supplies a continuous voltage of 2.658 V with the efficiency of 85.46%, which is sufficient to power for small devices such as remote environment sensors, temperature sensors, LED lighting, and submersible ultrasonic receiver.     

Effect of sediment microbial fuel cell stacks on 9 V/12 V DC power supply

Sediment microbial fuel cell (SMFC) is a bio-electrochemical device that uses anaerobic bacteria to produce renewable energy. The voltage generated by SMFC is very low, so directly it cannot be applied to modern electronic devices. But, it is feasible to raise the output voltage of SMFC by connecting them in series-parallel combinations. In the present work, four SMFC modules are developed in the laboratory and by connecting in four different ways the output voltage as well as the output current are raised to the utility levels. The primary cause to avoid the practical application of series and parallel connected SMFC is voltage reversal problem. To do away with this problem, in this work each group of SMFCs is first used to charge a super-capacitor (4 F, 5.5 V) and then it has been used to power the dc boost converter. Moreover, in this research work, the effects of charging and discharging times of super capacitors for each module are also investigated. In the final stage, a dc boost converter is presented to step-up the voltage of stacked SMFCs which provides a regulated output voltage (9 V/12 V) at the load. The results obtained, show that module-4 connected boost converter provides higher output current for a longer duration as compared to other super capacitor connected modules. This technique of energy harvesting from SMFCs can be used as a power source (either of 9 V or 12 V) in practical electronic devices.     

Power management system for a 2.5 W remote sensor powered by a sediment microbial fuel cell

One of the challenges in using wireless sensors that require high power to monitor the environment is finding a renewable power source that can produce enough power. Sediment microbial fuel cells (SMFCs) are considered an alternative renewable power source for remote monitoring, but current research on SMFCs has demonstrated that they can only produce several to tens of mW of continuous power. This limits the use of SMFCs as an alternative renewable remote power source to mW-level power. Such low power is only enough to operate a low-power sensors. However, there are many remote sensors that require higher power, on the order of watts. Current technology using a SMFC to power a remote sensor requiring watts-level intermittent power is limited because of limitations of power management technology. Our goal was to develop a power management system (PMS) that enables a SMFC to operate a remote sensor consuming 2.5 W of power. We designed a custom PMS to store microbial energy in capacitors and use the stored energy in short bursts. Our results demonstrate that SMFCs can be a viable alternative renewable power source for remote sensors requiring high power.     

Powering a wireless temperature sensor using sediment microbial fuel cells with vertical arrangement of electrodes

The application of wireless sensors is an important approach for monitoring natural water systems in remote locations; however, limited power sources are a key challenge for successful application of these sensors. Sediment microbial fuel cells (SMFCs) have shown potential as a sustainable power source with low maintenance requirements to power wireless sensors. This study examines electricity generation in lab-scale SMFCs with the sediment from Lake Michigan. Two SMFCs are operated in parallel with a difference in cathode arrangement (floating cathode vs. bottom cathode). The data show that the SMFC with a floating cathode produces more electricity and results in a shorter charging time when an ultracapacitor is connected to the circuit. To control electricity delivery and voltage elevation to a value that can drive a wireless temperature sensor, a power management system (PMS) is developed. With the PMS, both SMFCs can consistently power the wireless temperature sensor for data transmission to a computer, although the number of recorded data within the same period differs. This research provides an effective PMS for power control and valuable experience in SMFC configurations for the next onsite test of the developed SMFCs in Lake Michigan.     

Power management strategies for a stand-alone power system using renewable energy sources and hydrogen storage

A stand-alone power system based on a photovoltaic array and wind generators that stores the excessive energy from renewable energy sources (RES) in the form of hydrogen via water electrolysis for future use in a polymer electrolyte membrane (PEM) fuel cell is currently in operation at Neo Olvio of Xanthi, Greece. Efficient power management strategies (PMSs) for the system have been developed. The PMSs have been assessed on their capacity to meet the power load requirements through effective utilization of the electrolyzer and fuel cell under variable energy generation from RES (solar and wind). The evaluation of the PMS has been performed through simulated experiments with anticipated conditions over a typical four-month time period for the region of installation. The key decision factors for the PMSs are the level of the power provided by the RES and the state of charge (SOC) of the accumulator. Therefore, the operating policies for the hydrogen production via water electrolysis and the hydrogen consumption at the fuel cell depend on the excess or shortage of power from the RES and the level of SOC. A parametric sensitivity analysis investigates the influence of major operating variables for the PMSs such as the minimum SOC level and the operating characteristics of the electrolyzer and the fuel cell in the performance of the integrated system.     

Energy management of fuel cell/battery/supercapacitor hybrid power source for vehicle applications

This paper proposes a perfect energy source supplied by a polymer electrolyte membrane fuel cell (PEMFC) as a main power source and storage devices: battery and supercapacitor, for modern distributed generation system, particularly for future fuel cell vehicle applications. The energy in hybrid system is balanced by the dc bus voltage regulation. A supercapacitor module, as a high dynamic and high power density device, functions for supplying energy to regulate a dc bus voltage. A battery module, as a high energy density device, operates for supplying energy to a supercapacitor bank to keep it charged. A FC, as a slowest dynamic source in this system, functions to supply energy to a battery bank in order to keep it charged. Therefore, there are three voltage control loops: dc bus voltage regulated by a supercapacitor bank, supercapacitor voltage regulated by a battery bank, and battery voltage regulated by a FC. To authenticate the proposed control algorithm, a hardware system in our laboratory is realized by analog circuits and numerical calculation by dSPACE. Experimental results with small-scale devices (a PEMFC: 500-W, 50-A; a battery bank: 68-Ah, 24-V; and a supercapacitor bank: 292-F, 30-V, 500-A) corroborate the excellent control principle during motor drive cycle.     

Fuel-cell powered uninterruptible power supply systems: Design considerations

A 1-kVA fuel cell powered, line-interactive uninterruptible power supply (UPS) system that employs modular (fuel cell and power converter) blocks is introduced. Two commercially available proton-exchange membrane fuel cell (25–39 V, 500 W) modules together with suitable dc–dc and dc–ac power electronic converter modules are employed. A supercapacitor module is also used to compensate for the instantaneous power fluctuations and to overcome the slow dynamics of the fuel processor (reformers). Further energy stored in the supercapacitor is also utilized to handle a momentary overload such as 200% for a short duration. Due to the absence of batteries, the system satisfies the demand for an environmentally clean source of energy. A complete design that defines the amount of hydrogen storage required for a power outage of 1 h, and the sizing of the supercapacitors for transient load demand is presented for a 1-kVA UPS.     

Energy management of PEM fuel cell/ supercapacitor hybrid power sources for an electric vehicle

This paper presents the utilization of a supercapacitor (SC) as an auxiliary power source in an electric vehicle (EV), composed of a proton electrolyte membrane fuel cell (PEMFC) as the main energy source. The main weak point of PEMFC is slow dynamics because one must limit the fuel cell current slope in order to prevent fuel starvation problems, to improve its performance and lifetime. The very fast power response and high specific power of a supercapacitor can complement the slower power output of the main source to produce the compatibility and performance characteristics needed in a propulsion system. DC-DC converters connected to the hybrid source ensure a constant voltage value in inverters inputs. After an architecture presentation of the hybrid energy source, two parallel-type configurations are explored in more detail. For each of them, the energy flow control and management, validated simulation shows the performance obtained in this configuration. The hybrid source management is based primarily on the intervention of the supercapacitor in fugitives' schemes such as slopes, different speeds and rapid acceleration. Secondly, the PEMFC intervenes to guarantee the power in permanent regime. Finally, simulation results considering energy management are presented and illustrated the hybrid energy source benefits.     

Energy management of fuel cell/solar cell/supercapacitor hybrid power source

This study presents an original control algorithm for a hybrid energy system with a renewable energy source, namely, a polymer electrolyte membrane fuel cell (PEMFC) and a photovoltaic (PV) array. A single storage device, i.e., a supercapacitor (ultracapacitor) module, is in the proposed structure. The main weak point of fuel cells (FCs) is slow dynamics because the power slope is limited to prevent fuel starvation problems, improve performance and increase lifetime. The very fast power response and high specific power of a supercapacitor complements the slower power output of the main source to produce the compatibility and performance characteristics needed in a load. The energy in the system is balanced by d.c.-bus energy regulation (or indirect voltage regulation). A supercapacitor module functions by supplying energy to regulate the d.c.-bus energy. The fuel cell, as a slow dynamic source in this system, supplies energy to the supercapacitor module in order to keep it charged. The photovoltaic array assists the fuel cell during daytime. To verify the proposed principle, a hardware system is realized with analog circuits for the fuel cell, solar cell and supercapacitor current control loops, and with numerical calculation (dSPACE) for the energy control loops. Experimental results with small-scale devices, namely, a PEMFC (1200 W, 46 A) manufactured by the Ballard Power System Company, a photovoltaic array (800 W, 31 A) manufactured by the Ekarat Solar Company and a supercapacitor module (100 F, 32 V) manufactured by the Maxwell Technologies Company, illustrate the excellent energy-management scheme during load cycles.     

Evaluation of fluctuating voltage topology with fuel cells and supercapacitors for automotive applications

To develop a single‐stage power conversion topology in which energy storage devices can be directly coupled, a fluctuating voltage topology is applied, leading to lower cost and more compactness with the absence of DC/DC converters. This paper investigates such a topology for automotive applications where fuel cells are directly connected to the DC bus of the inverter, resulting in fluctuating voltage across the DC bus. Further, a supercapacitor pack is also introduced to maintain the power capacity and voltage stability. The hybridization principle and practical application of such a topology are then discussed in the time domain and frequency domain. Furthermore, the transient power requirement is decomposed to design the size of fuel cells and supercapacitors. Simulation results from the modeling of the fuel cell‐supercapacitor powertrain demonstrate the feasibility and effectiveness of this topology. The supercapacitors can serve as a low‐pass filter for the fuel cells. In conclusion, the peak power requirement can be successfully achieved because of the lowered system impedance, and the fuel cells only need to supply the average power.     

Power performance improvement in sediment microbial fuel cells: Recent advances and future challenges

Sediment microbial fuel cells (SMFCs) provide a promising sustainable technological platform that has been proposed for multiple applications, including sediment bioremediation and power sources for environmental sensors. However, the practical applications of SMFC are restricted due to their limited output power. This review analyzes the limitations on output power and their causes. Then, a variety of strategies proposed to improve the power performance of SMFC, ranging from electrode modification to SMFC configuration optimization and energy harvesting strategies, are summarized and discussed in detail. Finally, future challenges and perspectives are analyzed, with an expectation that SMFC technology can be further advanced. This review aims to provide insights into power performance improvement and practical applications of SMFC.     

Effects of unit distance and number on sediment microbial fuel cell stacks for practical power supply

Sediment microbial fuel cells (SMFCs) can covert the biomass and organic matters in sediments into electricity. SMFC stack is an essential way for the application of SMFCs. The unit distance and number will be crucial for SMFC stacks applied in practical environments. This study showed that the power density of individual SMFC increased with the unit distance when compared with SMFCs with a small distance. For hydraulically connected serial stacks, increasing unit distance from 2 to 28 cm decreased the potential loss from 50.4% to 11.3%, but the power output did not increase with either unit distance or number of units due to higher internal resistance and electrode reversal. For hydraulically connected parallel stacks, increasing unit number from one to three multiplied the power output but no further power increase was observed with four and five units, indicating an optimal unit number (OUN) in parallel stacks due to ion conduction. Similar performance was shown when using SMFC stacks to power a light‐emitting diode and an environmental sensor. The results provide important information for improving the power and cost‐effectiveness of SMFC stacks.     

Improvement of sediment microbial fuel cell performances by design and application of power management systems

One of the ways to generate clean and non-destructive energy is to use the energy stored in the biomass resources by the microbial fuel cells (MFCs). Sediment Microbial Fuel Cells (SMFCs) are a special type of MFCs that use organic materials in aquifers sediment to generate electricity. In this research, the effects of an increase in the electrode surface are investigated. The results showed that the increase in cathode electrode surface had better efficiency than the multi-cathode mode (maximum power generated for a 3-cathode electrode (27 cm³) and 1-cathode electrode (27 cm³) was 526 mW/cm² and 800 mW/cm², respectively. Another parameter affecting the performance of these systems is temperature. In the next step, the power generation rate was measured in different step currents and at different sample times. In the final stage, a power management system (PMS) was designed to optimally utilize the output energy of the improved SMFC, leading to an increase in the output voltage to 3.3 V.     

Electric power generation based on variable speed wind turbine under load disturbance

This study was interested in the management of an energy production unit. A variable speed wind turbine (VSWT) was used as a principal source and a supercapacitor (SC) module was used as an energy storage system. Both were connected through a direct current bus. This unit was supplying a three-phase load using an inverter and an inductor and capacitor filter. In order to regulate the direct current bus voltage, the SC storage state was controlled by using a buck-boost converter according to load instructions and wind speed fluctuations. Then, a resonant controller was established to avoid any disturbances and to control the alternating line-to-line voltages of the load which may be unbalanced. This study has shown that the stability of the three-phase voltage source depends on the direct current bus power management and also on the line-to-line voltage control. Simulation results are presented to validate the efficiency of the control strategies used.     

Anthraquinone modified carbon fabric supercapacitors with improved energy and power densities

Supercapacitors with improved energy and power densities have been constructed with anthraquinone modified carbon fabric (Spectracarb 2225) as the negative electrode and unmodified carbon fabric as the positive electrode. A Nafion separator and 1 M sulfuric acid electrolyte were employed. The performances of the supercapacitors were characterized by cyclic voltammetry and constant current discharging. Use of the anthraquinone modified electrode as the negative electrode (anode during discharge) in the supercapacitor provides 40% higher average capacitance, 56–86% higher energy density, and improved power duration.     

A power allocation strategy of a hybrid energy storage system for a PV grid-connected system

针对光伏并网系统中光伏微电源出力的波动性和间歇性,将蓄电池和超级电容器构成的混合储能系统HESS（hybrid energy storage system）应用到光伏并网系统中可以实现光伏功率平滑、能量平衡以及提高并网电能质量。在同时考虑蓄电池的功率上限和超级电容的荷电状态（SOC）的情况下,对混合储能系统提出了基于超级电容SOC的功率分配策略;该策略以超级电容的SOC和功率分配单元的输出功率作为参考值,对混合储能系统充放电过程进行设计。超级电容和蓄电池以Bi-direction DC/DC变换器与500 V直流母线连接,其中超级电容通过双闭环控制策略对直流母线电压进行控制。仿真结果表明,所提功率分配策略能对混合储能系统功率合理分配,而且实现了单位功率因数并网,稳定了直流母线电压。     

Influence of temperature and electrolyte on the performance of activated-carbon supercapacitors

For hybrid electric vehicle traction applications, energy storage devices with high power density and energy efficiency are required. A primary attribute of supercapacitors is that they retain their high power density and energy efficiency even at −30 °C, the lowest temperature at which unassisted starting must be provided to customers. More abuse-tolerant electrolytes are preferred to the high-conductivity acetonitrile-based systems commonly employed. Propylene carbonate based electrolytes are a promising alternative. In this work, we compare the electrochemical performance of two high-power density electrical double layer supercapacitors employing acetonitrile and propylene carbonate as solvents. From this study, we are able to elucidate phenomena that control the resistance of supercapacitor at lower temperatures, and quantify the difference in performance associated with the two electrolytes.     

Agent-based power sharing scheme for active hybrid power sources

The active hybridization technique provides an effective approach to combining the best properties of a heterogeneous set of power sources to achieve higher energy density, power density and fuel efficiency. Active hybrid power sources can be used to power hybrid electric vehicles with selected combinations of internal combustion engines, fuel cells, batteries, and/or supercapacitors. They can be deployed in all-electric ships to build a distributed electric power system. They can also be used in a bulk power system to construct an autonomous distributed energy system. An important aspect in designing an active hybrid power source is to find a suitable control strategy that can manage the active power sharing and take advantage of the inherent scalability and robustness benefits of the hybrid system. This paper presents an agent-based power sharing scheme for active hybrid power sources. To demonstrate the effectiveness of the proposed agent-based power sharing scheme, simulation studies are performed for a hybrid power source that can be used in a solar car as the main propulsion power module. Simulation results clearly indicate that the agent-based control framework is effective to coordinate the various energy sources and manage the power/voltage profiles.     

Evaluating the performance of microbial fuel cells powering electronic devices

A microbial fuel cell (MFC) is capable of powering an electronic device if we store the energy in an external storage device, such as a capacitor, and dispense that energy intermittently in bursts of high-power when needed. Therefore its performance needs to be evaluated using an energy-storing device such as a capacitor which can be charged and discharged rather than other evaluation techniques, such as continuous energy dissipation through a resistor. In this study, we develop a method of testing microbial fuel cell performance based on storing energy in a capacitor. When a capacitor is connected to a MFC it acts like a variable resistor and stores energy from the MFC at a variable rate. In practice the application of this method to testing microbial fuel cells is very challenging and time consuming; therefore we have custom-designed a microbial fuel cell tester (MFCT). The MFCT evaluates the performance of a MFC as a power source. It uses a capacitor as an energy storing device and waits until a desired amount of energy is stored then discharges the capacitor. The entire process is controlled using an analog-to-digital converter (ADC) board controlled by a custom-written computer program. The utility of our method and the MFCT is demonstrated using a laboratory microbial fuel cell (LMFC) and a sediment microbial fuel cell (SMFC). We determine (1) how frequently a MFC can charge a capacitor, (2) which electrode is current-limiting, (3) what capacitor value will allow the maximum harvested energy from a MFC, which is called the “optimum charging capacitor value,” and (4) what capacitor charging potential will harvest the maximum energy from a MFC, which is called the “optimum charging potential.” Using a LMFC we find that (1) the time needed to charge a 3-F capacitor from 0 to 500 mV is 108 min, (2) the optimum charging capacitor value is 3 F, and (3) the optimum charging potential is 300 mV. Using a SMFC we find that (1) the time needed to charge a 3-F capacitor from 0 to 500 mV is 5 min, (2) the optimum charging capacitor value is 3 F, and (3) the optimum charging potential is 500 mV. Our results demonstrate that the developed method and the MFCT can be used to evaluate and optimize energy harvesting when a MFC is used with a capacitor to power wireless sensors monitoring the environment.     

Advances in supercapacitors: From electrodes materials to energy storage devices

随着绿色储能器件的快速发展,超级电容器作为兼具高比能量与高比功率的优点,在储能领域具有重要发展潜力的新型储能器件,本综述从超级电容器的电极材料出发,详细概括了超级电容器电极材料的发展,包括双电层电容材料、赝电容材料以及双电层/赝电容复合材料;在此基础上,基于固态电解质,深入讨论了近年来全固态超级电容器的典型构型,针对性地总结了提高储能器件储能容量的关键问题。最后,基于电极材料与电解液的研究焦点,对超级电容器的研究提出了未来发展方向。